1. Field of the Invention
This invention is directed to a rotary handle mechanism for a circuit interrupting device, and more particularly to a door release for such a mechanism used with a circuit breaker mounted in an enclosure.
2. Background of the Invention
Circuit interrupters (e.g., circuit switching devices, circuit breakers, etc.) are generally old and well-known in the art. Examples of circuit breakers are disclosed in U.S. Pat. No 4,489,295; 4,638,277; 4,656,444 and 4,679,018. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload and relatively high level short circuit condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an overcurrent condition.
A common type of circuit switching device has a front face with a manual handle which may be arcuately operated between an on position and an off position. A common type of circuit breaker has a similar handle which is connected to movable contacts through a spring powered, over center toggle device which trips the contacts open and moves the handle to an intermediate trip position in response to certain overcurrent conditions. A fourth, reset position, which is beyond the off position and opposite from the on position, is used to reset a trip mechanism of the circuit breaker following a trip condition.
For a variety of reasons, such as operator safety, circuit interrupters are commonly mounted behind a panel or behind a door in a cabinet. Typically in these installations, the circuit interrupter handles are not directly accessible by the operator. In some of these installations, where the circuit interrupter handle is not located directly behind the panel or door, a remote handle mechanism drives one end of a flexible shaft in a linear push-pull manner. A rod at the other end of the flexible shaft is used to drive a sliding operating mechanism in a similar linear push-pull fashion. The sliding operating mechanism is mounted on the front face of the circuit interrupter and has a hole for inserting the circuit interrupter handle therethrough. The linear motion of the sliding operating mechanism is used to simulate the arcuate motion of the circuit interrupter handle.
In other such installations, where the circuit interrupter is installed inside an enclosure having a door and the circuit interrupter handle is suitably located behind the door, an external mechanism including a rotary handle is mounted to the opposite side of the door. A mechanical linkage, such as a rigid shaft, is used to interconnect the rotary handle with a pivot mechanism inside the enclosure. The pivot mechanism drives a sliding mechanism which moves the circuit interrupter handle between the on, off and reset positions.
During maintenance of such circuit interrupters, the enclosure door is opened by moving the rotary handle to its reset position. In the reset position, a latch in the rotary handle disengages the shaft and, hence, the door may be opened. For relatively large circuit interrupters, the reset operation, for example, may require between about 65 and 160 pounds of force. Such force is transmitted through the rotary handle to the shaft and, in turn, to the circuit interrupter handle. The resulting torque causes friction between the rotary handle and the shaft. Accordingly, the enclosure door is difficult to open.
There is a need, therefore, for a remote operating mechanism for an enclosure-mounted circuit interrupter which permits an enclosure door to freely open in the reset position of the circuit interrupter.